Practice Essentials

Pediatric febrile seizures, which represent the most common childhood seizure disorder, exist only in association with an elevated temperature. Evidence suggests, however, that they have little connection with cognitive function, so the prognosis for normal neurologic function is excellent in children with febrile seizures.
[1]

Epidemiologic studies have led to the division of febrile seizures into 3 groups, as follows:

In a case-series analysis of a cohort of 323,247 US children born from 2004 to 2008, Hambidge et al found that delaying the first dose of measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine beyond the age of 15 months may more than double the risk of postvaccination seizures in the second year of life.
[2, 3]

In infants, there was no association between vaccination timing and postvaccination seizures.
[3] In the second year of life, however, the incident rate ratio (IRR) for seizures within 7-10 days was 2.65 (95% confidence interval [CI], 1.99-3.55) after first MMR doses at 12-15 months of age, compared with 6.53 (95% CI, 3.15-13.53) after first MMR doses at 16-23 months. For the MMRV vaccine, the IRR for seizures was 4.95 (95% CI, 3.68-6.66) after first doses at 12-15 months, compared with 9.80 (95% CI, 4.35-22.06) for first doses at 16-23 months.

Signs and symptoms

Simple febrile seizure

The setting is fever in a child aged 6 months to 5 years

The single seizure is generalized and lasts less than 15 minutes

The child is otherwise neurologically healthy and without neurologic abnormality by examination or by developmental history

Fever (and seizure) is not caused by meningitis, encephalitis, or any other illness affecting the brain

The seizure is described as either a generalized clonic or a generalized tonic-clonic seizure

Complex febrile seizure

Age, neurologic status before the illness, and fever are the same as for simple febrile seizure

This seizure is either focal or prolonged (ie, >15 min), or multiple seizures occur in close succession, i.e. within the same fever episode

Diagnosis

No specific laboratory studies are indicated for a simple febrile seizure. Physicians should instead focus on diagnosing the cause of fever. Other laboratory tests may be indicated by the nature of the underlying febrile illness. For example, a child with severe diarrhea may benefit from blood studies for electrolytes.

With regard to lumbar puncture, the following should be kept in mind:

Strongly consider lumbar puncture in children younger than 12 months, because the signs and symptoms of bacterial meningitis may be minimal or absent in this age group

Lumbar puncture should be considered in children aged 12-18 months, because clinical signs and symptoms of bacterial meningitis may be subtle in this age group

In children older than 18 months, the decision to perform lumbar puncture rests on the clinical suspicion of meningitis

Management

On the basis of risk/benefit analysis, neither long-term nor intermittent anticonvulsant therapy is indicated for children who have experienced 1 or more simple febrile seizures.

If, however, preventing subsequent febrile seizures is essential, oral diazepam would be the treatment of choice. It can reduce the risk of febrile seizure recurrence and, because it is intermittent, probably has the fewest adverse effects.
[4]

Antipyretics have typically been suggested with a primary goal of comfort in mind, as it has been uncertain whether antipyretics can impact the occurrence of further febrile seizures. However a randomized controlled trial published in 2018 suggested that rectal acetaminophen given every 6 hours may prevent febrile seizure recurrence within the same febrile episode.
[5]

Background

Febrile seizures are the most common seizure disorder in childhood. Since early in the 20th century, people have debated about whether these children would benefit from daily anticonvulsant therapy. Epidemiologic studies have led to the division of febrile seizures into 3 groups, as follows: simple febrile seizures, complex febrile seizures, and symptomatic febrile seizures.

Simple febrile seizure

See the list below:

The setting is fever in a child aged 6 months to 5 years.

The single seizure is generalized and lasts less than 15 minutes.

The child is otherwise neurologically healthy and without neurological abnormality by examination or by developmental history.

Fever (and seizure) is not caused by meningitis, encephalitis, or other illness affecting the brain.

Complex febrile seizure

See the list below:

Age, neurological status before the illness, and fever are the same as for simple febrile seizure.

This seizure is either focal or prolonged (ie, >15 min), or multiple seizures occur in close succession i.e. during the same febrile episode.

Symptomatic febrile seizure

See the list below:

Age and fever are the same as for simple febrile seizure.

The child has a preexisting neurological abnormality or acute illness.

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Pathophysiology

This is a unique form of seizures that occurs in early childhood and only in association with an elevation of temperature. The underlying pathophysiology is unknown, but genetic predisposition clearly contributes to the occurrence of this disorder.
[6]

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Frequency

United States

Febrile seizures occur in 2-5% of children aged 6 months to 5 years in industrialized countries. Among children with febrile seizures, about 70-75% have only simple febrile seizures, another 20-25% have complex febrile seizures, and about 5% have symptomatic febrile seizures.

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Mortality/Morbidity

See the list below:

Children with a previous simple febrile seizure are at increased risk of recurrent febrile seizures; this occurs in approximately one third of cases.

Children younger than 12 months at the time of their first simple febrile seizure have a 50% probability of having a second seizure. After 12 months, the probability decreases to 30%.

Children who have simple febrile seizures are at a slightly increased risk for epilepsy. The rate of epilepsy by age 25 years is approximately 2.4%, which is about twice the risk in the general population.

The literature does not support the hypothesis that simple febrile seizures are associated with lower intelligence or learning disability or are associated with increased mortality
[7] .